Wireless device

ABSTRACT

A wireless multi-band device comprises a radiating system comprising a ground plane layer, a boosting element, and a radiofrequency system, wherein the radiofrequency system comprises a tunable reactive element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.18/087,315 filed Dec. 22, 2022, which is a continuation of U.S. patentapplication Ser. No. 17/244,486 filed Apr. 29, 2021, now U.S. Pat. No.11,563,461, issued Jan. 24, 2023, which is a continuation of U.S. patentapplication Ser. No. 16/160,613 filed Oct. 15, 2018, now U.S. Pat. No.11,018,712, issued on May 25, 2021, which is a continuation of U.S.patent application Ser. No. 15/404,969 filed Jan. 12, 2017, now U.S.Pat. No. 10,122,403, issued on Nov. 6, 2018, which claims priority under35 U.S.C. § 119(e) from U.S. Provisional patent application Ser. No.62/277,541, filed Jan. 12, 2016, the entire contents of which are herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the field of wireless devices, forexample wireless portable and/or handheld devices which require thetransmission and reception of electromagnetic wave signals and to aradiating system for such wireless devices.

BACKGROUND

Wireless devices and radiating systems for them typically operate one ormore cellular communication standards and/or wireless connectivitystandards, each standard being allocated in one or more frequency bands,and said frequency bands being contained within one or more regions ofthe electromagnetic spectrum. Examples for such wireless devices includea mobile phone, a smartphone, a PDA, an MP3 player, a headset, a USBdongle, a laptop computer, a gaming device, a digital camera, a PCMCIAor Cardbus 32 card, or generally a multifunction wireless device.

The invention relates in particular to wireless devices (and radiatingsystems), which can perform in two or more separate frequency regions(bands) of the electromagnetic spectrum. They are generally referred toas multi-band devices (radiating systems), and are in particular forexample referred to as dual-band (working in two frequency bands),tri-band (working in three frequency bands), quad-band (working and fourfrequency bands) and penta-band (working in five frequency bands).Standards, according to which such wireless devices (radiating systems)may operate, comprise for example UMTS, GSM (e.g., GMS850, GSM900,GSM1800, GSM1900) and LTE (e.g., LTE700, LTE2300, LTE2500). Thenecessary frequency bands may thus, for example, comprise the frequencyregions in the areas from 800 MHz to 960 MHz and from 1710 MHz to 2690MHz, or from 698 MHz to 960 MHz and from 1710 to 2690 MHz.

It is known in the art to use wireless devices (radiating systems) thatdo not require the use of a separate antenna element, but rather use aground plane layer providing a determined radioelectric performance inone or more frequency regions of the electromagnetic spectrum. Suchdevices are also referred to as antennaless devices because they do nothave a separate antenna element. Such devices (radiating systems) are,for example, known from co-owned applications W02010/15365,W02010/15364, WO 2014/012796 and U.S. Ser. No. 14/807,449. Thedisclosures of the aforementioned co-owned applications are herewithincorporated by reference in their entirety. In case of conflict, thepresent specification, including definitions, will control.

Such (antennaless) devices typically comprise a radiating system capableof transmitting and receiving electromagnetic wave signals in at leasttwo frequency regions. The radiating system comprises a radiatingstructure comprising at least one ground plane layer and at least oneboosting element. The radiating system further comprises aradiofrequency system. The radiofrequency system is suitable to modifythe impedance of the radiating structure to provide impedance matchingto the radiating system in the at least first and second frequencyregions of operation of the radiating system.

In well matched radiating systems, the reflection coefficient may have avalue of approximately −4 dB or less, for example −4.5 dB or less, inparticular −6 dB or less in the frequency region in which the wirelessdevice operates. In other well matched radiating systems, the voltagestanding wave ratio (VSWR) may be 4.5 or less, in particular 4 or less.Such radiofrequency systems typically provide their impedance matchingby using a radiofrequency system with long and complex matching networksof electronic components comprising a large number of passive reactivecomponents, for example 6 or more components. Such radiofrequencysystems are known, for example, from the above-mentioned, co-ownedapplications. In addition to the matching network, the radiofrequencysystem may, for example, comprise additional switches, diodes or otherelements or no other elements, i.e., the radiofrequency system mayconsist of the matching network.

SUMMARY

The invention comprises a wireless multi-band device comprising aradiating system capable of transmitting and receiving electromagneticwave signals in at least two frequency regions (frequency bands), theradiating system comprising a radiating structure comprising at leastone ground plane layer and at least one boosting element and aradiofrequency system suitable to modify the impedance of the radiatingstructure, thus providing impedance matching to the radiating system inthe at least first and second frequency regions of operation of theradiating system, wherein the radiofrequency system comprises a tunablereactive element. In particular, the tunable reactive element may becomprised in the matching network, wherein the matching network iscomprised by the radiofrequency system. Such a matching network may beused because the boosting element or boosting elements may be (severely)out of tune for the frequency regions in which the wireless device isdesigned to operate.

Examples for radiating structures which may be used in a wirelessmulti-band device (also referred to as wireless device in the following)can, for example, be seen in FIGS. 4, 8, 12, 17, 19 and 21 to 25 ofWO2010/015365.

Examples for boosting elements which may be used in a radiating systemcomprise radiation boosters as disclosed in WO 2010/015365, for exampleradiation boosters as shown in FIGS. 16, 19, 20, 23 . Other boostingelements which may be used in the radiating system are also sold underthe name mXTEND™, BAR mXTEND™, RUN mXTEND™ antenna boosters. Forexample, such a radiation booster, antenna booster or boosting elementmay (for example in all directions or in three directions which are eachorthogonal to the other) have a maximum size (extension) of smaller than1/30 or 1/50 times the free-space wavelength corresponding to the lowestfrequency of the lowest frequency band in which the wireless multi-banddevice is configured to perform. They may, for example, in alldirections of space have an extension (length) of smaller than 1/30 or1/50 times the free-space wavelength corresponding to the lowestfrequency of the lowest frequency band in which the wireless multi-banddevice is configured to perform. Such radiation boosters or antennaboosters may not radiate significantly themselves. For example, theirown radiation my result in a radiation efficiency below 35% when theyare mounted and tested on a large ground plane (e.g., larger than awavelength in diameter or side for the longest operating wavelength, forinstance a 600 mm×600 mm squared ground plane) in a vertical monopoleconfiguration at the center of such a ground plane. In some cases,radiation boosters or antenna boosters might feature a radiationefficiency as low as 10%, 5%, 2% or even lower when tested in thoseconditions at the longest operating wavelength. The longest operatingwavelength is the free-space wavelength corresponding to the lowestfrequency of the lowest frequency band in which the wireless multi-banddevice is configured to perform. The radiation booster or antennabooster may, under these conditions, be so poorly matched (no matchingnetwork included in such a test), that the overall antenna efficiency(i.e., including the mismatch loss in the efficiency computation) mightbe as low as 5% or lower, or even below 1% or 0.5% at the longestoperating wavelength.

Other examples for boosting elements may be larger and have somecontribution to the radiation on their own. They may, for example, be atthe edge of booster technology and at the edge of antenna technology.For example, they may have a size between 1/6 and 1/30 of the longestoperating wavelength (i.e., their length in all directions of space mayhave an extension (length) of smaller than between 1/6 and 1/30 timesthe free-space wavelength corresponding to the lowest frequency of thelowest frequency band in which the wireless multi-band device isconfigured to perform), and feature a radiation efficiency between 20%and 50% and an antenna efficiency between 10% and 35% when tested as avertical monopole in a large ground plane (e.g., 600×600 mm) as in theconditions as set above. This is in contrast with typical antennas thatare typically a quarter wavelength or longer and may feature a radiationefficiency above 50%.

One, two, three or more boosting elements, for example radiationboosters or antenna boosters, may be used in a radiating system, inparticular the matching network comprised by the radiating system. Eachof them may be configured as the above-mentioned radiation boosters ofthe prior art or one of the other mentioned examples. Optionally, in asystem comprising two or more or exactly two boosting elements, thesemay be interconnected by a lumped reactive component, e.g., an inductoror a capacitor. In some embodiments, one boosting element only may becomprised in the radiating system.

With such a tunable reactive element, the number of components used inthe radiofrequency system, in particular in the matching network, may bereduced and/or the number of necessary boosting elements may be reducedand/or improved impedance matching may be provided.

For example, only one boosting element and a radiofrequency systemcomprising a matching network with two or three reactive componentscomprising (at least) one tunable reactive component may be sufficientto match the radiating system in two frequency regions.

In particular, a tunable reactive element may allow adjusting of theworking frequency by changing the tunable reactive element, shifting thefrequency on which the wireless device (radiating system) works best tothe preferred frequency area, for example a particular band or a channelthereof (each frequency band may comprise several channels in whichdevices can communicate with each other).

In particular, it may allow obtaining a radiating system working acrossa wide range of mobile/wireless frequency bands and/or it may make thedesign of the system easier due to fewer components. The system may bemore stable in view of the fact that with a larger number of components,the tolerances of the components add up, and that the overall radiationefficiency of the entire radiating system increases as the number ofcomponents decreases. Due to the reduced mismatch, the correspondinglosses may be reduced, for example from 6 dB to 10 dB, resulting in anincreased ground-plane antenna efficiency, for example in the amountfrom 75% to 90% or approximately 1 dB in improvement.

A tunable reactive element in a radiating system, in particular in thematching network, may allow further reduction of the size of theboosting elements, reducing the necessary clearance area around theboosting elements, and it may allow overlapping boosting elements ontothe ground plane layer to use small ground planes and platforms due tothe reduced number of elements. This may, in particular, lead to smallerradiating systems and smaller wireless devices. In known systems,(severely) reducing the clearance area around a boosting element mayresult in a reduction of the impedance bandwidth of the system and mayresult in an unacceptable bandwidth in passive, fixed systems. With atunable reactive element in the radiating system, such a narrowerbandwidth can be moved and located with the tuning mechanism (e.g., byself-tuning) to the frequency region of interest, i.e., the frequencyregion of operation. This may be sufficient because a passive, fixedsystem typically does not use the entire bandwidth at the same time.

Such a tunable reactive element may, for example, comprise or be atunable (i.e., variable) capacitor. Possible capacitors that may be usedin such a radiating system may have a capacity in a range or comprisinga range from 0.6 pF to 2.35 pF or may have a capacity comprising part ofsaid range. Possible tunable capacitors which may, for example, be usedcomprise Cavendish SmarTune™ Antenna Tuners, e.g., 32CK301, 32CK417,32CK402, 32CK503, 32CK505, Peregrine e.g., PE64905, PE64909, ONSemiconductor-ParaScan or TCP-3012H.

Alternatively or additionally, such a tunable reactive element maycomprise or be a tunable inductor. Such tunable inductors may, forexample, be implemented by using a switch and a bank of fixed inductors.They may have an inductivity in a range or comprising a range from 2 nHto 30 nH or may have an inductivity comprising part of said range.

For example, a radiofrequency system or the matching network comprisedby it may comprise a passive reactive component and a tunable reactivecomponent. In some examples, the radiofrequency system or the matchingnetwork comprised by it may consist of one passive reactive componentand one tunable reactive component, i.e., it may not comprise any otherreactive components. The passive reactive component(s) may optionally belumped component(s). These components may be arranged in parallel in theradiofrequency system or the matching network comprised by it. In otherembodiments, they may be arranged in series.

In other examples, a radiofrequency system or the matching networkcomprised by it may comprise two passive reactive components and atunable reactive component. These passive reactive components mayoptionally be lumped components. In some examples, the radiofrequencysystem or the matching network comprised by it may consist of twopassive reactive components and one tunable reactive component, i.e., itmay not comprise any other reactive components. For example, one passivecomponent may be switched in series with parallel arrangement of anotherpassive reactive and the tunable reactive component.

The wireless device may be programmed to self-tune itself whenever thedetected performance is below a certain threshold. For example, when auser (or a disrupting device) blocks a boosting element or modifies thefrequency by influencing the wireless device in some other manner (forexample by hand or finger blocking the booster), the system may notice areduction in performance and self-tuning may adjust the system such thatthe performance is improved. For example, the wireless device may beprogrammed to measure the total received power and/or the total radiatedpower and, when measuring a reduction in performance, to self-tune theradiating system. In another example, the wireless device may beprogrammed to self-tune by changing the tunable reactive component insearch for a maximum of the total received power and/or the totalradiated power in certain time intervals or according to a triggerevent.

Wireless devices (radiating systems) may, in particular, be antennaless,i.e., they may not have a separate antenna element in addition to theground plane layer. Such antennaless configurations with aradiofrequency system suitable to modify the impedance of the radiatingstructure, providing impedance matching to the radiating system in theat least first and second frequency regions of operation of theradiating system, are known from the prior art, in particular theco-owned applications mentioned above.

A wireless multi-band device (radiating system) may comprise a controlmechanism for controlling the tunable reactive element. The controlmechanism may be adapted for tuning the tunable reactive element suchthat the wireless device operates in an (at least one) intendedfrequency band by changing the reactivity of the tunable reactiveelement.

The information about the intended frequency band may be provided by auser and/or found from signals received by the wireless device.Alternatively or in addition, the control device may be adapted toself-tune the wireless device, for example when the detected performanceis below a certain threshold or changes during wireless communicationwith another device.

The control mechanism may, for example, direct the self-tuning of thewireless device by receiving information about an intended frequencyband and/or performance of the wireless device, processing thisinformation and tuning the tunable reactive element based on thereceived information. The control mechanism may comprisecomputer-readable instructions saved on a computer-readable device that,when carried out by a processor or microprocessor (for example aprocessor or microprocessor comprised in the wireless multi-band device)direct the wireless multi-band device to carry out the above describedmethod steps of receiving information about an intended frequency bandand/or performance of the wireless device, processing these informationand tuning the tunable reactive element based on the receivedinformation.

The invention also comprises a multi-band radiating system (for use in awireless device) comprising a ground plane layer, a boosting element anda radiofrequency system characterized in that the radiofrequency systemcomprises a tunable reactive element. Such a multi-band radiating systemmay in particular be a radiating system as described above, and may beconfigured as a radiating system described above.

For example, it may be capable of transmitting and receivingelectromagnetic wave signals in at least two frequency regions(frequency bands) and/or may comprise a tunable capacitor and/or atunable inductor, and/or its tunable reactive element may consist of atunable capacitor or tunable inductor. The multi-band radiating systemmay be antennaless, i.e., they may not have a separate antenna elementin addition to the ground plane layer and/or may comprise a boostingelement which is smaller than 1/30 time the free-space wavelengthcorresponding to the lowest frequency of the lowest frequency band inwhich the multi-band radiating system is configured to perform and/orthe radiofrequency system may consist of one or two passive and atunable reactive element and/or its tunable reactive element may beadapted to be tuned by a control mechanism adapted for tuning it suchthat the wireless device operates in an intended frequency range.

The values to be used for the particular components to be used in asystem, e.g., depending on the ground plane shape and size, the usedboosting element and other known parameters may, for example, be foundusing ordinary tools for simulating such systems, e.g., CAD tools suchas Microwave Office.

For example, for a (very small) boosting element, in a first stage ofdetermining the values, a first inductor may be used to place theresonance frequency in between the high and low frequency regions (e.g.,between 699-960 MHz and 1710-2690 MHZ). In a second stage, a pair of apassive inductor and tunable capacitor (or other tunable combination oftwo reactive elements, e.g., of a tunable inductor and a passivecapacitor or a combination of a tunable inductor and a tunablecapacitor) may be used to fine-tune the impedance of the system in thetwo regions. A CAD tool may be used to select the range of values of thetunable element(s) to finely match the impedance in the desired regions.In other examples, the inductor used in the first step may be tunable oran (optionally tunable) capacitor or an (optionally tunable) combinationof reactive elements may be used instead of the (optionally tunable)inductor. Correspondingly, in the second stage, one (optionally tunable)reactive component may be used instead of a combination.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments will now be described with reference to the figures.

FIG. 1 a shows an example for a wireless device 100 comprising a groundplane layer 152, a radiation booster 151 and a radiofrequency system153.

FIGS. 1 b, 1 c, and 1 d show two different examples for ground planelayers that may be used in a wireless device according to the invention.

FIG. 1 e shows an excerpt of an example for a ground plane layer thatmay be used in a wireless device according to the invention.

FIG. 2 a shows a radiofrequency system according to the prior art.

FIGS. 2 b and 2 c show radiofrequency systems which may be used in awireless device according to the present invention.

FIGS. 3 a, 3 b, 3 c, 3 d, 3 e and 3 f show a comparison of a reflectioncoefficient of the prior art with reflection coefficient of aradiofrequency system tuned to different values.

FIG. 4 a shows a radiofrequency system according to the prior art.

FIGS. 4 b and 4 c show radiofrequency systems which may be used in awireless device according to the present invention.

FIGS. 5 a, 5 b, 5 c, 5 d, and 5 e show a comparison of a reflectioncoefficient of the prior art with an exemplary reflection coefficient ofa radiofrequency system tuned to different values.

DETAILED DESCRIPTION

FIG. 1 a shows a wireless device 100. In this particular example, thewireless device is a cell phone comprising a radiating system with aground plane layer 152, a boosting element 151 and a radiofrequencysystem 153. The particular example shown in FIG. 1 a is antennaless,i.e., it does not have a separate antenna element in addition to theground plane layer. In other embodiments, the wireless device may be adifferent wireless device, for example one of the wireless devicesmentioned above.

FIGS. 1 b and 1 c show examples for ground plane layer and boostingelement arrangements which can be used in exemplary wireless multi-banddevices.

For example, ground plane layers used in radiating systems may have asize between 100 mm and 160 mm in one direction (length) and between 40mm and 80 mm in a direction perpendicular to it (width). Ground planelayers typically have, i.e., for example, less than 1/10 of the widthand/or length, for example, less than 1/100 of the width and/or length.Ground plane layers used in smartphones may, for example have a sizebetween 50 to 60 mm in width and between 120 and 150 mm in length. Theymay, for example, have a rectangular shape.

The ground plane layer may be printed on a dielectric layer or material.The dielectric layer may, for example, be between 0.5 mm and 4 mm high.As long as the ground plane layer fits on the dielectric layer, itslength and width can have arbitrary values in any size. Typically, bothlength and width of the dielectric layer are much larger than the heightof the dielectric layer, for example it may have a width of between 40mm and 120 mm and a height between 100 mm and 180 mm. If a dielectricmaterial is used, it typically has a flat surface in at least the areato which the ground plane layer is printed. Dielectric layers andmaterials which may be used for this may, for example, comprise FR4 orother similar materials, and these materials may have a relativepermittivity (dielectric constant) of between 3.8 and 4.5, for example arelative permittivity of approximately 4.15. The tangent of the lossangle δ (tan δ) of the dielectric layer or material may have a value inan area between 0.005 and 0.03, in particular between 0.011 and 0.015,in particular for example approximately 0.013.

The boosting elements may have a greatest length of between, forexample, 15 mm and 35 mm.

In the example of FIG. 1 b , the ground plane layer 142 may have a sizeof approximately 120 mm in length and 60 mm in width and may, forexample, be printed on a 1 mm high FR4 layer with a permittivity ofapproximately 4.15. The tangent of the loss angle δ may approximately be0.013 (tan δ=0.013). Other sizes for the ground plane layer and/or theboosting element and/or the ground plane layer being printed on adifferent material are also comprised by the invention.

FIG. 1 b also shows an exemplary clearance area 143 around the boostingelement 141 which extends along nearly the entire width of the groundplane layer 142 (with the exception of a small strip 144). Such a smallstrip 144 may have in one direction (e.g., its width, which along thesame direction as the width of the ground plane layer) an extension ofless than 1/10 of the width of the clearance area 143 (width againconsidered in the same direction as the width of the ground planelayer). This small strip 144 serves to connect the boosting element 141with the ground plane layer 142. The strip may, for example, have asubstantially straight or L-shaped form. It may follow the externalcontour of a printed circuit board (PCB) on which it may be present. Insome embodiments, a portion of the strip may be curved to follow a patharound a mechanical obstacle such as a screw, a post, an electroniccomponent or the like.

The boosting element 141 may have dimensions of between 10 mm to 14 mmby 1 mm to 5 mm by 0.4 mm to 4.4 mm. For example, it may be a RUNAntenna booster, and it may have dimensions of approximately 12 mm×3mm×2.4 mm in the particular example shown in FIG. 1 b.

To match such a radiating system as shown in FIG. 1 b , for example forthe frequency regions 824-960 MHz and 1710-2690 MHz, six passivecomponents are needed. In FIG. 2 a , an example for a prior artradiofrequency system is shown. The indicated capacities andinductivities are exemplary. Other values may be used in otherembodiments.

FIG. 2 b shows a radiofrequency system with a tunable capacitor. Thiscan, for example, be used for matching a system as shown in FIG. 1 b .In the system shown in FIG. 2 b , the capacitor is tunable (the value of1.311 pF is only one example for possible values).

FIG. 2 c shows schematically how to couple three reactive elements 1, 2and 3 for a radiofrequency system, wherein one is a tunable capacitor 1(variable capacitor C_(var)) and two are passive reactive components, inthis case inductors 2 and 3, in order to provide a radiofrequency systemfor a radiating system according to FIG. 1 b . In particular, the leftconnection point of FIG. 2 c may be connected with the boosting element.The right connection point may be connected to the transceiver orinput/output of the radiofrequency system of the wireless device.

Here, the inductor 2 is coupled in series with a system comprising aparallel arrangement of an inductor 3 and the tunable capacitor 1.

FIGS. 3 a to 3 f show how the reflection coefficient changes dependingon the capacitance value of the tunable capacitor.

In particular, FIGS. 3 a to 3 f each show a comparison of a reflectioncoefficient for a radiofrequency system as of FIG. 2 a (marked by X)with the reflection coefficient achieved with a matching systemaccording to FIG. 2 b (marked by rectangles) for a single value ofcapacitance of the tunable capacitor.

The capacitance of the corresponding tunable capacitor is 1.6 pF forFIG. 3 a, 1.1 pF for FIG. 3 b, 0.95 pF for FIG. 3 c, 0.8 pF for FIG. 3d, 0.58 pF for FIG. 3 e , and 0.45 pF for FIG. 3 f . In FIG. 3 a , theradiating system operates in the frequency region corresponding to theGSM1800 standard, in FIG. 3 b , the radiating system operates in thefrequency region corresponding to the GSM850 and GSM1900 standard, inFIG. 3 c , the radiating system operates in the frequency regioncorresponding to UMTS, in FIG. 3 d , the system operates in thefrequency region corresponding to the GSM900 standard, and in FIG. 3 ein the frequency region corresponding to the LTE2300 standard. In FIG. 3f , the system operates in the frequency region corresponding to theLTE2500 standard.

With three reactive components 1, 2, and 3, it is possible to match from824-960 MB and from 1710-2690 MHz. In addition, for several frequencystandards, for example GSM850, GSM900, and GSM1800 and LTE2500, thesystem comprising a tunable reactive element provides better matchingthan the solution using only passive components. Such a better matchingmay, in particular, result in better antenna efficiency. In addition, aradiofrequency system with a tunable reactive element may reduce thelosses due to matching processes because a reduced number of componentsis used in comparison with the passive reactive elements solution.

In the system according to FIG. 2 c , when considering the inputimpedance of the system with a single L series, capacitive impedance ispresent for low frequency regions, for example the frequency regionsbetween 824-960 MHz. At the same time, there is an inductive impedancefor high frequency regions, for example 1710-2690 MHz.

For low frequency regions, a single L series has to be used to bring theimpedance into resonance, for the high frequency region, a capacitor hasto be used. In examples of wireless multi-band devices, an LC-shunt isused in series with an inductor. For the low frequency region, thecombination of LC is equal to C, for the high frequency region, it isequal to L. Since there is a tunable capacitor in this shunt, theradiofrequency systems has enough degrees of freedom to match both thelow frequency region and the high frequency region.

FIG. 1 c shows a ground plane layer and boosting element alternative tothe one of FIG. 1 b . In FIG. 1 c , the ground plane layer 132exemplarily has a size of 120 mm in one direction and of 60 mm in adirection perpendicular to it, is printed on a 1 mm high layer of FR4, apermittivity of 4.15 and tan δ=0.013, and the boosting element 131 hasthe form of a rectangular box with the length of 20 mm, a width of 3 mm,and a height of 1 mm. Other sizes for the ground plane layer and/or theboosting element and/or the ground plane layer being printed on adifferent material are also comprised by the invention.

FIG. 1 c also shows an exemplary clearance area 133 around the boostingelement 131 which extends along nearly the entire width of the groundplane layer 132 (with exception of a small strip 134). Such a smallstrip 134 may have in one direction (e.g., its width, measured in thesame direction as the width of the ground plane layer) an extension ofless than 1/10 of the width of the clearance area 133 (width againconsidered in the same direction as the width of the ground plane layer)and serves to connect boosting element 131 with the ground plane layer132.

According to the prior art, for the matching such a radiating system, aradiofrequency system comprising at least six (lumped) components isrequired to match such a boosting element in several frequency regionsin the areas 698-960 MHz and 1710-2690 MHz. FIG. 4 a shows a prior artradiofrequency for matching such a system. Here, seven (lumped)components are shown. However, the inductive component LP=81 nH can beneglected, such that matching may also be achieved with six (lumped)components.

When using a tunable capacitor, matching in the areas between 698-960MHz and 1710-2690 MHz can be achieved using one (passive) inductor 2 andone tunable capacitor 1, as shown for example in FIG. 4 b andschematically in FIG. 4 c . FIG. 4 b shows a particular example of aradiofrequency system including examples for particular values that maybe used. In the example of FIG. 4 b , the capacitor is tunable. In otherexamples, one tunable inductor and one (passive) capacitor may be used(not shown).

Corresponding reflection coefficients for such a system are shown inFIGS. 5 a to 5 e . Herein, the capacitance varies from 1.38 pF in FIGS.5 a to 1 pF in FIG. 5 b, 0.86 pF in FIG. 5 c, 0.56 pF FIG. 5 d , and 0.4pF in FIG. 5 e.

FIGS. 5 a to 5 e show how the reflection coefficient changes dependingon the capacitance value of the tunable capacitor.

In particular, FIGS. 5 a to 5 d each show a comparison of a reflectioncoefficient for a radiofrequency system as of FIG. 4 a (marked bytriangles) with the reflection coefficient achieved with a matchingsystem according to FIG. 4 b (marked by rectangles) for a single valueof capacitance of the tunable capacitor.

FIG. 5 a shows matching in the areas of GSM1800 and GSM1900 and thefrequency range between 698 MHz and 750 MHz, FIG. 5 b shows a matchingin the frequency region of 750 MHz to 798 MHz, FIG. 5 c shows a matchingto the frequency region used by the UMTS standard, FIG. 5 d in thefrequency region used for LTE2300, and FIG. 5 e in the frequency regionused for LTE2500.

FIG. 1 d shows another ground plane layer and boosting elementalternative. In FIG. 1 d , the ground plane layer 152 has a reducedclearance area 153 with regard to the one in FIGS. 1 b and 1 d extendingover nearly the entire width of the ground plane layer. In FIG. 1 d ,also a remaining strip 154 of the ground plane layer connecting theground plane layer and the booster.

FIG. 1 e shows another ground plane layer and boosting elementalternative in which the boosting element is arranged overlapping ontothe ground plane layer.

As can be seen, the use of a tunable reactive element in aradiofrequency system may improve the matching and/or reduce the numberof boosting elements and/or reduce the number of components of theradiofrequency system.

What is claimed is:
 1. A wireless device comprising: a ground planelayer having a maximum size smaller than half of a longest free-spaceoperating wavelength of the wireless device; a boosting element having alargest dimension smaller than 1/6 times the longest free-spaceoperating wavelength; and a radiofrequency system comprising a tunablereactive circuit including: a switch connected between the boostingelement and a transceiver, and a bank of fixed matching networks,wherein at least a portion of an orthogonal projection of the boostingelement onto a plane containing the ground plane layer overlaps theground plane layer.
 2. The wireless device of claim 1, wherein amatching within the bank of fixed matching networks comprises a seriesinductor.
 3. The wireless device of claim 1, wherein a matching withinthe bank of fixed matching networks comprises a parallel LC circuit. 4.The wireless device of claim 1, wherein the boosting element has alargest dimension smaller than 1/10 times the longest free-spaceoperating wavelength.
 5. The wireless device of claim 1, wherein theboosting element has a largest dimension smaller than 1/20 times thelongest free-space operating wavelength.
 6. The wireless device of claim1, wherein the boosting element has a largest dimension smaller than1/30 times the longest free-space operating wavelength.
 7. The wirelessdevice of claim 1, wherein the ground plane layer has a maximum sizesmaller than 1/3^(rd) of the longest free-space operating wavelength. 8.The wireless device of claim 1, wherein the ground plane layer has amaximum size smaller than 1/4^(th) of the longest free-space operatingwavelength.
 9. The wireless device of claim 1, wherein the ground planelayer has a maximum size smaller than 1/5^(th) of the longest free-spaceoperating wavelength.
 10. The wireless device of claim 1, wherein theground plane layer has a maximum size smaller than 1/10^(th) of thelongest free-space operating wavelength.
 11. The wireless device ofclaim 1, wherein the wireless device operates in two frequency regions.12. The wireless device of claim 11, wherein the wireless deviceoperates in a first frequency region from 698 MHz to 960 MHz and in asecond frequency region from 1710 MHz to 2690 MHz.
 13. A wireless devicecomprising: a ground plane layer having a maximum size smaller than halfof a longest free-space operating wavelength of the wireless device; aboosting element having a largest dimension smaller than 1/6 times thelongest free-space operating wavelength; and a radiofrequency systemcomprising a matching network including a tunable reactive element,wherein at least a portion of an orthogonal projection of the boostingelement onto a plane containing the ground plane layer overlaps theground plane layer.
 14. The wireless device of claim 13, wherein thematching network includes three reactive elements.
 15. The wirelessdevice of claim 14, wherein the matching network includes an inductorconnected in series with a parallel arrangement of circuit elementsincluding a tunable capacitor and an inductor.
 16. The wireless deviceof claim 13, wherein the matching network includes a tunable capacitor.17. The wireless device of claim 13, wherein the matching networkincludes a tunable capacitor arranged in parallel with an inductor. 18.The wireless device of claim 13, wherein the matching network includes atunable inductor and a passive capacitor.
 19. The wireless device ofclaim 18, wherein the tunable inductor comprises a switch and a bank offixed inductors.
 20. The wireless device of claim 13, wherein thematching network includes a tunable inductor and a tunable capacitor.